Again! both for me and another rust question for this forum, My dodge,a 99 qc 1500 4x4, like some is rusting. Areas include Front driver side fender "bad" ,passenger side is starting and bellow both doors and the top of the body under the doors. I have already attempted to fix the fender, sanded down,, used "phoscperic acid" of sorts then primer and paint+clear, yet only a few weeks later it was bubbling through now six months later it is now rust spots, There were places that i had to use a small amount of bondo but no backing as they were no bigger then a quarter once i punched it through. What i am asking is does this sound like it is rusting from the insideout.....If so can this be fixed? i am thinking new fenders would be the easiest but at 250 a peice not the cheapest and how can i make sure that the rust wouldnt comeback? thnx

P.S. Live in michigan and go to school at Michigan Tech so "salt" doesnt help the issue

 

Check out my thread I did. Your probably not taking enough of the rust off when you fix it, and your not using a good enough Primer. You need to yuse a really good primer made specificially to stop rust thats already started.
https://dodgeforum.com/m_813981/tm.htm

P.S. I live in Michigan too, and I go to MTU too haha, Small world

 

+1 on Socha's thread. Great write-up!